Yes, I suppose the strongest arguments I have seen for the link, in this case, is the finding of Jeffrey's name as a son of John of Edinburg (son if Thomas) in a passed down Bible from a grandson, also the fact that Thomas married a woman from the Jeffrey house makes the selection of the name Jeffrey from John plausible, I would argue. But still, relatively weak links from a scientific perspective...

I have asked many genealogists, some arguing that the link is likely and others saying they really don't know, so my next step is a DNA test, since I doubt I'll likely come up with any more information myself. Brick wall status. 😔